A power supply typically converts an alternating current source to a direct current source for use by electronic devices. The architecture and operation of a power supply can introduce harmonics and cause differences between the phase of a voltage provided by the alternating current (AC) source and the phase of a current drawn from the AC source, reducing the power factor and, consequently, the efficiency, of the power supply. A power factor correction circuit, such as a boost converter, can be used to correct, or improve, the power factor of a power supply by reducing these phase differences and offsetting the effects of the harmonics. For example, an inductor in a boost converter circuit can be switched between a charging state and discharging state at a frequency, and with a modulated duty cycle, selected to, among other things, cause the power supply to generate a generally constant output voltage while causing the average current flowing through the inductor to align with, or to match, an expected inductor current (e.g., a current that is in phase with the AC source voltage). Since current through the inductor is drawn from the AC source, aligning the average inductor current with the AC source voltage can cause the AC source current to align with the AC source voltage, improving the power factor of the power supply. The power factor, and the overall efficiency, of the power supply can be further improved by interleaving the operation of, for example, two boost converters.
Industry regulations and device requirements can require a power supply to maintain a regulated output voltage for a threshold period of time (e.g., a holdup time) during fault conditions in the AC source (e.g., dropouts in the AC source voltage). Techniques for meeting these requirements can include adding energy storages devices (e.g., capacitors) to a power supply to extend holdup time during input supply faults. The added energy storage devices, however, can increase the size and costs the power supply. Additionally, the added energy storage devices can reduce power supply efficiency by reducing their power factor of a power supply. For example, storage capacitors added to the output of a power supply to extend holdup time can contribute to a phase difference between the AC source voltage provided to the power supply and AC source current drawn by the power supply.